Metmyoglobin Reducing Capacity of Fresh Normal, PSE, and DFD Pork During Retail Display

Fresh pale, soft, exudative (PSE), dark, firm, dry (DFD), and normal pork were stored under light or dark conditions at 4°C for 7 days. Sample pH, metmyoglobin reductase activity, oxygen consumption rate, and relative surface metmyoglobin and oxymyoglobin contents were determined. DFD pork had the highest metmyoglobin reductase activity and oxygen consumption rate. Enzyme activity of PSE was lower than that of normal pork, but no difference existed in oxygen consumption rate between PSE and normal samples. Metmyoglobin reductase activity dropped slowly during meat storage; oxygen consumption rate sharply decreased during the first day of storage. Both metmyoglobin reductase activity and oxygen consumption rate declined more rapidly in the light. Results can help develop guidelines for display and packaging of pork.     

畜禽宰后肌肉能量代谢与肉品质研究进展

畜禽宰后肌肉通过糖酵解等能量代谢途径提供ATP满足能量需要,产物乳酸的生成会降低pH。糖酵解的速度和程度影响了pH的下降速度和程度,进而调控肉品色泽、嫩度、持水性、多汁性、风味等品质。本文综述了畜禽宰后肌肉能量代谢的基本路径,论述了腺苷酸激活蛋白激酶对糖酵解的调控机理及其对肉品质的影响,并着重叙述了白肌肉(pale soft and exudative meat,PSE)的预防措施,为在生产过程中肉品质调控提供思路。     

软冷冻和臭氧处理对猪肉的保鲜效果比较

为了提高肉类等食品在冰箱软冷冻条件下的贮藏效果,研究以新鲜猪肉为原料,设定软冷冻（－7 ℃）＋臭氧组（Ⅰ）、软冷冻（－7 ℃）组（Ⅱ）、－18 ℃冷冻组（Ⅲ）3 个低温保藏环境,通过测定pH值、菌落总数、挥发性盐基氮含量、新鲜度K值及感官评价比较分析猪肉新鲜度及品质变化。结果表明：－7 ℃软冷冻在21 d内可以保持肉的品质在一级鲜度,35 d保持在二级鲜度,有利于家庭应用;软冷冻结合臭氧可以将一级鲜度延长至45 d,降低pH值和菌落总数,且与－18 ℃冻藏相比能有效保持猪肉色泽,可以用于商品化生产。     

ATP Metabolites During Aging of Exudative and Nonexudative Pork Meats

ABSTRACT: The content of nucleotide metabolites in the muscle L.dorsi from 9 exudative and 9 acceptable quality pork carcasses was determined during 7 d of aging in order to establish a period postmortem for detecting exudative meats. Hypoxanthine and inosine levels in exudative meats were different (p < 0.05) from those of normal meats up to 3 days of aging, while 5'-inosine monophosphate (IMP) and 5'-adenosine triphosphate (ATP) contents only differed during the 1st 4 and 6 h postmortem, respectively. The IMP/ATP ratio was only different (p < 0.05) at 2 h. Thus, 2 h postmortem is proposed as the optimal sampling time for the detection of exudative pork meats.     

鲜猪肉中磺胺类抗生素残留的检测与分析

采用高效液相色谱法（HPLC）对64份来自某城市市区及郊区鲜肉市场的生鲜猪肉样品中10种磺胺类抗生素的残留进行检测。结果显示,磺胺类抗生素的检出率和超标率分别为20.31%和10.94%,其中郊区的检出率和超标率均高于城区。10种磺胺类药物中检出率最高的是磺胺嘧啶（SD）,为7.81%,其次是磺胺甲二唑（SMT）和磺胺吡啶（SP）,分别为6.25%和4.69%。此结果表明,部分鲜猪肉中磺胺类抗生素的残留量较高,有诱发产生耐药菌的潜在威胁,相关部门应加强指导养殖业抗生素的合理使用。     

Consumer-rated Quality Characteristics as Related to Purchase Intent of Fresh Pork

Consumers (n=556) rated pink color, wet/dry appearance, overall acceptability and purchase intent of normal, pale, soft and exudative (PSE), and dark, firm and dry (DFD) pork loin slices in PVC packages in five retail supermarkets. DFD samples appeared driest and PSE samples appeared wettest. Samples in the higher ranked two purchase intent categories appeared more wet than those in the lower three categories. The pinker PSE samples and all DFD samples were in the higher ranked purchase intent categories. Purchase intent generally paralleled overall acceptability; however, prediction equations indicated that wet/dry appearance, color and overall acceptability all contributed to purchase intent decision depending on muscle condition.     

影响猪肉皮气膨化涨发的关键工艺因素研究

目的:通过对影响猪肉皮气膨化涨发的关键要素的研究,得出气膨化涨发干猪肉皮最佳工艺的涨发温度和时间.方法:先采用单因素分析法,通过色泽、组织状态、香味、弹性感官品质进行感官鉴定得出第1阶段不同烤制温度、第1阶段不同烤制时间、第2阶段不同烤制温度的工艺参数,再用正交试验法得出气膨化涨发猪肉皮的最佳值.结果:猪肉皮气膨化最佳涨发条件是:先上火90℃、下火100℃烤40min,后上、下火230℃的烤至完全膨化.其中,影响猪肉皮气膨化涨发的关键因素依次是第2阶段的烤制温度>第1阶段烤制温度>第1阶段烤制时间     

Early Postmortem Detection of Exudative Pork Meat Based on Nucleotide Content

The content of nucleotide metabolites in the muscle L. dorsi was analyzed for the detection of pale, soft and exudative (PSE) pork meats at just 2 h postmortem. PSE meat was characterized by significantly lower (p < 0.05) amounts of adenosine 5'-triphosphate (ATP) and higher adenosine 5'-monophosphate (AMP), inosine 5'-monophosphate (IMP), inosine (ino) and hypoxanthine (hyp) than normal meat. IMP and ino classified all the samples from both groups with statistical significance (p < 0.05). The K₀ value, R' value and IMP/ATP ratios were also useful indicators for full distinction of PSE meats. Thus, the assay of any of these nucleotide metabolites may allow a good detection of PSE meats at very short, only 2 h, postmortem time.     

Acceptability and Shelf-life of Marinated Fresh and Precooked Pork

Fresh (FL) and precooked (PL) longissimus chops and fresh semi-membranosus/adductor (SM) roasts were evaluated to determine acceptability of marinated pork. Citric acid and sodium acid pyrophosphate lowered pH (CAP), sodium acid pyrophosphate attained intermediate pH (SAP), and sodium tripolyphosphate increased pH (TPP). In FL and SM cuts, TPP improved sensory characteristics, water-holding capacity (WHC) and processing yields. CAP reduced microbial growth in FL chops and improved tenderness in SM roasts. In PL cuts, TPP improved juiciness and reheating yields. Marinating at low pH reduced microbial growth; marinating at high pH improved sensory properties, WHC, fresh pork processing yields and precooked pork juiciness and reheating yields.     

Konjac Flour Gel as Fat Substitute in Low-fat Prerigor Fresh Pork Sausage

Prerigor trimmings from four lean cuts of pork carcasses (n = 3) were used to manufacture three replications of low-fat (10%) fresh pork sausage containing konjac flour gel, at 0, 10 or 20% levels and compared to a 40% fat control. Treatment sausages showed equal or improved cooked yields, slightly higher shear force (kg/g) and sensory textural attributes, but rated slightly lower in juiciness. As konjac flour gel levels increased, shear force and sensory textural attributes became more like the control. Storage time had minimal effect on quality and shelf life. Acceptable low-fat, prerigor pork sausage can be produced with 10–20% incorporation of konjac flour gel.     

正常肉和白肌肉的蛋白质变化

测定白肌肉(Pale,Soft,Exudative,PSE)和正常猪肉(Reddish-pink,Firm,Non-exudative)持水性指标和在宰后不同时间的蛋白溶解性和蛋白降解程度。结果显示:PSE肉的各种蛋白溶解性都显著低于正常肉(p<0.05),宰后4 h的总蛋白、肌浆蛋白和肌原纤维蛋白的溶解性与滴水损失和贮藏损失都呈显著负相关,与持水力呈显著正相关。正常肉和PSE肉的肌浆蛋白和肌原纤维蛋白的SDS-PAGE电泳条带存在差异,PSE肉早期伴肌动蛋白(Nebulin)含量明显低于正常肉。可见PSE肉肌原纤维的降解较快,宰后早期的蛋白溶解性可以用于预测猪肉的持水性。     

生鲜猪肉中沙门氏菌的分离、鉴定及耐药性检测

调查本地区生鲜猪肉中沙门氏菌的污染情况及耐药性情况,为进一步对肉及肉制品中耐药性沙门氏菌的风险评估奠定基础。采集超市和集贸市场的生鲜猪肉,采用实时荧光定量PCR对生鲜猪肉中沙门氏菌污染进行初筛,然后根据沙门氏菌检验国家标准进行分离鉴定,并对分离到的沙门氏菌进行耐药性检测。结果从83份肉样中分离到21株沙门氏菌,沙门氏菌检出率为25.3%。21株沙门氏菌中有7株对11种抗生素中的至少一种产生耐药性,耐药率33.3%。结果表明本地区生鲜猪肉微生物污染较为严重,沙门氏菌检出率较高且四环素耐药严重;另外在菌落总数和沙门氏菌检出率方面冷却肉的质量好于热鲜肉,超市和集贸出售的肉的质量无显著差异。     

鲜猪肉微冻保鲜技术的初步研究

本文主要研究鲜猪肉在-2℃下微冻保鲜过程中的质量变化,为其商业微冻保鲜提供理论依据。首先通过冻结曲线以测定鲜猪肉的冰点为-1℃,再确定其冻结点为-2℃,然后将鲜猪肉在-2℃下进行微冻保鲜试验,每隔3天测一次感官指标、理化指标(pH值、持水力、T-VBN)、微生物指标,并对各种指标进行综合比较分析,来探讨微冻保鲜技术在鲜猪肉中应用的可行性。结果表明:随着贮藏天数的增加,细菌总数和pH值以及持水力都呈现先降后升的变化趋势,并保持较低的细菌总数、T-VBN值,其贮藏期限可达20d以上。     

降低冷鲜肉预冷损耗的研究

预冷损耗对于提高肉品质量,以及获得更好的经济效益具有重要的意义,本文就预冷间库温、预冷间湿度、风速对预冷损耗的影响进行了研究,探讨了合适的预冷工艺。     

猪背最长肌焦磷酸酶的分离纯化与酶学特性

通过离心、50%～70%饱和硫酸铵沉淀、DEAE-52离子交换柱层析,从猪背最长肌中分离纯化出焦磷酸酶(PPase)。变性聚丙烯酰胺凝胶电泳图谱显示,PPase分子质量约72kD。焦磷酸酶酶学特性研究表明,最适反应温度和pH值分别为50℃和7.5。Mg2+是PPase的激活剂,在浓度4.75mmol/L时,酶活力最强。但Na+和K+都能抑制酶的活力,且Na+的抑制效果强于K+。PPase水解焦磷酸钠(TSPP)的动力学参数Vmax为0.086μmol/(L.min)),Km为0.36mmol/L。     

Physicochemical and Sensory Qualities of Fresh Pork Chops as Affected by Phosphate, Ascorbate or Sorbate Dipping Prior to Irradiation

Fresh pork chops were dipped for a target absorption of 0.5% sodium tripolyphosphate (STPP), 550 ppm sodium ascorbate (SA), or 0.1% potassium sorbate (PS) prior to irradiation (1.0 kGy). Untreated pork chops, both irradiated and unirradiated, were used as controls. Dipping with STPP decreased drip loss and improved color and lipid stability of irradiated chops and resulted in better tenderness and juiciness scores than undipped, irradiated samples. Also, STPP treated chops had similar or better physicochemical and sensory properties than untreated (no irradiation, no dipping) controls. Dipping with SA or PS had little effect compared with STPP, but improved some sensory qualities.     

气调包装(MAP)在冷却肉保鲜中的应用

相比热鲜肉、冷冻肉,冷却肉具有安全系数高,营养价值高,保质期长的特点,是目前国外广泛应用的生鲜肉类销售形式,气调包装应用于冷却肉保鲜,能大大延长肉的保质期,并能很好地保持肉的色泽,本文阐述了气调包装保鲜机理及气体组分的研究进展,论述了气调包装的工艺要点及其设备发展现状,分析并提出了气调包装应用于冷却肉保鲜的关键技术和应用前景。     

不同温度贮藏热鲜猪肉品质变化比较

比较研究25、20、15、10℃和4℃五种贮藏温度下的热鲜猪肉在食用品质(蒸煮损失率、剪切力、肉色)、pH值、挥发性盐基氮(TVB-N)和微生物上的差异。结果表明:25、20℃和15℃热鲜肉无最佳消费时段,10℃和4℃最佳消费时段分别在36h和48～72h左右;25、20、15、10℃和4℃的热鲜肉一级鲜消费时段分别在12、18、36、48h和96h内。在48h内,10℃贮藏的热鲜肉与4℃贮藏相比,在蒸煮损失率、肉色(L值和a值)和TVB-N值方面无显著差异,且剪切力变化优于4℃贮藏的热鲜肉。     

生鲜冷却肉MAP包装保鲜技术的研究

应用MAP包装设备及技术研究生鲜冷却肉的保鲜,研究不同气氛条件下冷却肉的指标(感官性质、TVB-N、pH、菌落总数、货架期)。研究结果表明,CO2浓度为30%~40%,O2浓度为40%~60%时,对生鲜冷却肉有较好的保鲜效果,冷鲜肉MAP保鲜理想气氛条件为CO2%L∶O2%∶N2%=30∶50∶20,在4℃条件下储藏,货架期达8d以上。     

提高超市生鲜猪肉安全品质的几项措施

本文根据目前我国生鲜猪肉生产、屠宰加工和流通的实际情况，提出了改善生鲜猪肉安全品质的几项措施：为了以最快的方式进行追溯，建立了一套生鲜猪肉产销过程中的安全品质跟踪体系。